1. Field of the Invention
The present invention relates to a power transmission system for a vehicle, such as a cart or utility vehicle having a cargo deck, having front and rear transaxles and a prime mover disposed between the transaxles, wherein the power transmission system includes a power take-off from one of the front and rear transaxles, which is driven by the prime mover, and transmits the power to the other transaxle.
2. Related Art
Conventionally, there is a well known vehicle comprising a first transaxle for driving a first axle and a second transaxle for driving a second axle, the first and second transaxles being distributed before and behind a prime mover, such as an internal combustion engine, supported by a vehicle body frame. An input part of the first transaxle is disposed on one of left and right sides of the first transaxle so as to be drivingly connected to the prime mover through a transmission such as a continuously variable transmission (CVT). A power take-off part (a PTO part) is provided on the other right or left side of the first transaxle opposite to the first input part so as to be drivingly connected to an input part of the second transaxle through bevel gears and a propeller shaft, or so on. For example, such a vehicle is disclosed in the U.S. patent application Ser. No. 2001-4031 and the Japanese Patent Laid Open Gazette 2001-182562.
The first transaxle must be constructed so as to have the PTO part. Furthermore, the PTO part must be considerably laterally long, so that a drive train (such as a propeller shaft) extended from the PTO part to the input part of the second transaxle can be prevented from interfering with the prime mover between the first and second transaxles. Therefore, the first transaxle is complicated and expanded laterally, thereby increasing the cost.
To prevent the lateral expansion of the PTO part, it may be noticed that the drive train from the PTO part is just vertically offset from the prime mover. However, if the drive train is disposed below the prime mover, the vehicle may have insufficient ground clearance. Furthermore, the height of the first axle of the first transaxle and the transmission (CVT) restrain the raising or lowering of the PTO part. As a result, even if the drive train extended from the PTO part to a space above or below the engine is slanted steeply as far as possible, the vehicle still requires a considerably large space between the engine and the first transaxle in the fore-and-aft direction of the vehicle, thereby preventing the longitudinal length of the vehicle from being minimized. Further, there are many vehicles in each of which an operator's operation part is disposed between the prime mover and the second transaxle in the fore-and-aft direction. With regard to such a vehicle, the power transmission system for transmitting power from the PTO shaft of the first transaxle to the input part of the second transaxle must be arranged so as to secure enough space for the operation part.
These are the reasons why the conventional PTO part formed on the first transaxle is laterally elongated so that the drive train from the PTO part is laterally offset from the prime mover.
Further, the first transaxle may be disposed upright so as to reduce the fore-and-aft length of the vehicle. In this case, the intermediate shaft of the first transaxle is disposed above the first axles so that the intermediate shaft becomes considerably higher than the input part of the second transaxle. Accordingly, the bend angle of a universal joint used for connecting the intermediate shaft of the first transaxle to the input part of the second transaxle becomes large so as to increase intrusive noise and reduce comfort of the vehicle.
If a power take-off device for transmitting power from the first transaxle to the second axle, instead of the PTO part formed on the first transaxle, is separated from the first transaxle and laterally offset from the engine, the only requirement of the first transaxle is that one of transmission shafts in the first transaxle is simply extended so as to serve as a PTO shaft, thereby prompting standardization and cost-reduction of the first transaxle. Further, such a standardized first transaxle is desirable so as to be applicable to not only the four-wheel drive vehicle having the second axle driven by the first transaxle but also a two-wheel drive vehicle, whose second axle is not driven. If the first transaxle is used for a two-wheel drive vehicle, the above-mentioned PTO part does not have to be formed on the casing of the first transaxle. Further, it is preferable that the outwardly projecting PTO shaft and the opening for passing the PTO shaft are removed from the casing of the first transaxle when the first transaxle is used for a two-wheel drive vehicle.